Directional
detector
t
Timer
Low level
blocking
Blocking
logic
U3P
URES
IRES
I3P
RCA_CTL
U
2
Uo
Io
BLOCK
DIRECTION
RELEASE
I
2
Figure 729: Functional module diagram
Directional detector
When "Neg. seq. volt." selection is made using the
Pol quantity setting, the
Directional detector module compares the angle of the negative-sequence current
(I
2
) to the negative-sequence voltage (–U
2
). Using the negative-sequence voltage
angle as the reference, the negative-sequence current angle is compared to the
Characteristic angle setting. If the angle difference is within the operating sector
selected by
Direction mode setting, the Enable signal is sent to Timer.
The value of
Characteristic angle should be chosen in such way that all
the faults in the operating direction are seen in the operating zone and all
the faults in the opposite direction are seen in the backward zone.
The operating sector is defined by the settings
Max forward angle, Max reverse
angle, Min forward angle and Min reverse angle. The options that can be selected for
Directional mode settings are “Forward” and “Reverse”.
Characteristic angle is also known as Relay Characteristic Angle RCA, Relay Base
Angle or Maximum Torque Line.
Protection related functions
1MRS759142 F
1288
REX640
Technical Manual